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Fast Beam Diagnostics at the ILC Using the Beam Calorimeter

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Geant4 simulation with realistic b-field map and compare to simplified one. Hopefully no fast shower simulation has to be included (cpu time dependent) ... – PowerPoint PPT presentation

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Title: Fast Beam Diagnostics at the ILC Using the Beam Calorimeter


1
Fast Beam Diagnostics at the ILC Using the Beam
Calorimeter
  • Christian Grah, Desy
  • FCAL Workshop
  • 12-13 February
  • Cracow

2
Contents
  • Very forward region and BeamCal
  • Beam parameter reconstruction
  • Principle
  • Results on 20mrad geometry with the nominal ILC
    parameter set.
  • Summary and outlook

3
Very Forward Region
  • LumiCal 26 lt ? lt 82 mrad

BeamCal 4 lt ? lt 28 mrad
  • PhotoCal 100 lt ? lt 400 µrad

4
BeamCal
ee- pairs from beamstrahlung are deflected
into the BeamCal
Deposited energy from pairs at z 365 (no
B-field)
  • 15000 ee- per BX gt 10 20 TeV
  • 10 MGy per year
  • fast gt
    O(µs)
  • Direct photons for q lt 400 mrad (PhotoCal)

Wdiamond sandwich calorimeter
5
Backgrounds (Old 20mrad Geometry)
Sketch of old BeamCal geometry.
Projection of LumiCals inner radius.
Energy deposited in LumiCal from pairs.
6
ILC B-Field Configurations
20mrad DID (Ri(LumiCal) 13.5cm) (Ro(BeamCal)
16.5cm)
20mrad AntiDID (14mrad seems necessary for
AntiDID)
An AntiDID configuration is close to the
headon/2mrad design. BUT better be prepared for
both possibilities.
DID Detector integrated Dipole, B-field aligned
with the incoming beam AntiDID B-field aligned
with the outgoing beam
7
Fast Luminosity Monitoring
  • Why we need a fast signal from the BeamCal?
  • We can significantly improve L!
  • e.g. include number of pairs hitting BeamCal in
    the feedback system

Improves L by more than 12 (500GeV)!
position and angle scan
G.White QMUL/SLAC RHUL Snowmass presentation
Luminosity development during first 600 bunches
of a bunch-train. Ltotal L(1-600)
L(550600)(2820-600)/50
8
Beamstrahlung Pair Analysis
  • A lot of information is stored in the energy
    distribution of beamstrahlung pairs hitting
    BeamCal.
  • Observables (examples)
  • total energy
  • first radial moment
  • thrust value
  • angular spread
  • E(ring 4) / Etot
  • E / N
  • l/r, u/d, f/b asymmetries
  • Beam parameters
  • sx, sy, sz and ?sx, ?sy, ?sz
  • xoffset
  • yoffset
  • ?x offset
  • ?y offset
  • x-waist shift
  • y-waist shift
  • Bunch rotation
  • N particles/bunch
  • (Banana shape)

detector realistic segmentation, ideal
resolution, bunch by bunch resolution
9
Analysis Concept
  • Beam Parameters
  • determine collision
  • creation of beamstr.
  • creation of ee- pairs
  • guinea-pig
  • (D.Schulte)
  • Observables
  • characterize energy distributions in detectors
  • FORTRAN
  • analysis program (A.Stahl)
  • and/or
  • GEANT4

1st order Taylor-Exp.


Solve by matrix inversion (Moore-Penrose Inverse)
10
Coefficients of the Taylor-Matrix
observable j au
beam parameter i au
11
Analysis for nominal ILC Parameters
single parameter analysis
Quantity Nominal Value Precision Precision
old new
sx 553 nm 4.8 2.9
?sx 3.9 7.4
sy 5.0 nm 0.1 0.2
?sy 0.1 0.4
sz 300 mm 8.5 8.5
?sz 6.7 6.3
Dy 0 2.0 0.6
ILCNOM, 20mrad DID
12
2mrad and 20mrad Analysis
Quantity Nominal Value Precision Precision
2mrad 20mrad 20mrad (2par)
sx 553 nm 3.1 2.9 2.8
?sx 5.2 7.4 7.6
sy 5.0 nm 0.3 0.2 0.2
?sy 0.3 0.4 0.4
sz 300 mm 4.8 8.5 11.1
?sz 3.7 6.3 7.4
ey 40x10-9mrad 1.7 2.9 5.2
ey 0 4.2 4.1 4.7
Dx 17.7 9.3 10
Dy 0 0.5 0.6 0.6
N 2x1010 0.01 0.01 0.01
DN 0 0.01 0.02 0.03
...
13
Status of Analysis
  • GuineaPig files for ILCNOM ready (400 pair
    files).
  • New geometry ready.
  • Single and multiparameter analysis started.
    Mostly done for
  • 2mrad
  • 20mrad DID
  • Good progress in the Geant4 implementation
    (A.Sapronovs talk).

14
Summary Outlook
  • Including a fast signal of number of pairs or
    total energy into the feedback system can
    significantly increase luminosity of the
    accelerator.
  • Analyzing the spatial energy distribution of
    beamstrahlung pairs hitting the BeamCal grants
    access to many beam parameters. For highly
    correlated parameters measurements from other
    systems can be included (e.g. PhotoCal).
  • 20mrad geometry is implemented with DID field
    approximation.
  • ILCNOM investigation is in work.
  • Geant4 simulation is running, BC observable
    calculation and beam parameter reconstruction can
    be done with some limitations. Next
  • Geant4 simulation with realistic b-field map and
    compare to simplified one.
  • Hopefully no fast shower simulation has to be
    included (cpu time dependent). Fast shower
    simulation is implemented in Geant4 for
    homogenous detector.
  • Find most interesting regions (layers) in the
    BeamCal segments.
  • Need background calculation for our 20mrad
    geometry.
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